Fluid cooled injector and exhaust aftertreatment system, vehicle, and method using a fluid cooled injector

ABSTRACT

A fluid cooled injector includes an injector body comprising an injector tip and a cooling channel, the injector tip comprising an injector orifice, and a heat conducting shield, the heat conducting shield comprising a heat conducting shield orifice arranged coaxially with the injector orifice, the heat conducting shield being in direct contact with at least one of the injector body and the injector tip. An exhaust after treatment system and a vehicle including such an injector, and a method involving the use of such an injector, are also disclosed.

BACKGROUND AND SUMMARY

The present invention relates generally to fluid cooled injectors and,more particularly, to such injectors including heat shields tofacilitate heat transfer from the injector tip.

In exhaust aftertreatment systems for diesel engines, it is typical touse a so-called seventh injector to inject fuel into an exhaust streamto raise the temperature of the exhaust stream, usually for purposes ofregenerating a diesel particulate filter in the exhaust aftertreatmentsystem, although there are other circumstances when the seventh injectoris used to raise the temperature of the exhaust gas. In diesel enginesused in over-the-road trucks, these injectors tend to clog every20-40000 miles. Clogging of these injectors is problematic and in thepast, clogging has typically been addressed by conducting an air purge,which wastes time and fuel.

The inventors have discovered what they understand to be the mechanismbehind the clogging problem and have devised a simple solution toaddress the problem. The inventors realized that, when diesel fuel isheated to around 180-230° C., the fuel tends to become sticky and canadhere to surfaces. Further investigation revealed that the mixture ofsoot and fuel can bind strongly on a metal surface at this temperaturerange. Above the temperature range, the bonded mixture becomes loosedand will ordinarily easily come off the surface and, below thetemperature range, the mixture of soot and fuel will not ordinarilyadhere to the surface.

The inventors observed that temperatures around the seventh injector tipin vehicles can vary from about 100-280° C. depending upon engineapplication and running conditions. They believe that this explains whyclogging tends to occur for some vehicles, but not for others, becausethe temperature at the seventh injector tip varies. For certain vehiclesand conditions, the temperature around the seventh injector tip can bein the range of around 180-230° C. at which the fuel tends to becomesticky and adheres to surfaces, thus tending to clog the seventhinjectors in these vehicles.

It is desirable to provide a solution to the problem of seventh injectorclogging. It is also desirable to provide a solution that involveslittle or no extra use of fuel to overcome clogging problems, that isinexpensive to implement, and that is adapted to be retrofit on existingvehicles.

According to an aspect of the present invention, a fluid cooled injectorcomprises an injector body comprising an injector tip and a coolingchannel, the injector tip comprising an injector orifice, and a heatconducting shield, the heat conducting shield comprising a heatconducting shield orifice arranged coaxially with the injector orifice,the heat conducting shield being in direct contact with at least one ofthe injector body and the injector tip to transfer heat from theinjector tip to the cooled injector body.

According to another aspect of the present invention, a heat conductingshield for a fluid cooled injector is provided, the fluid cooledinjector comprising an injector body comprising an injector tip and acooling channel, the injector tip comprising an injector orifice. Theheat conducting shield comprises a first portion having a heatconducting shield orifice adapted to be arranged coaxially with theinjector orifice and a second portion, separate from the first pot atleast one of the first portion and the second portion being adapted tobe in direct contact with the injector body.

According to yet another aspect of the present invention, a method ofregenerating a diesel particulate filter (DPF) in an exhaustaftertreatment system is provided and includes injecting fuel into orupstream of the DPF through an injector orifice in an injector tip of aninjector, cooling a main body of the injector from which the injectortip extends by circulating a coolant through channels in the injector,and transferring heat from the injector tip via a heat conducting shieldin direct contact with at least one of the injector tip the main bodyaround the injector tip, and comprising a heat conducting Shield orificearranged coaxially with the injector orifice.

According to another aspect of the invention, the beat conducting shieldmay include a coating of a material to prevent fuel and exhaust matterfrom adhering to the shield. A suitable material may be Teflon® oranother non-stick coating. Preferably, the coating material is appliedto a surface of the heat conducting shield exposed to the exhaust gasflow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understoodby reading, the following detailed description in conjunction with thedrawings in which like numerals indicate similar elements and in which:

FIG. 1A is a schematic, cross-sectional view of an injector according toan aspect of the Present invention;

FIG. 1B is a schematic, cross-sectional view of a portion of an injectoraccording to an aspect of the present invention;

FIG. 2 is as cross-sectional view of a heat conducting shield accordingto an aspect of the present invention; and

FIG. 3 schematically shows an engine and a portion of an exhaustaftertreatment system according to an aspect of the present invention.

DETAILED DESCRIPTION

FIG. 1A shows a fluid cooled injector 21 according to an aspect of thepresent invention. The injector 21 comprises an injector body 23comprising an injector tip 25 and a cooling channel 27 through which acoolant (not shown) is circulated. The cooling channel 27 is ordinarilyring shaped and surrounds a central passage 28 leading to an injectororifice 29 in the injector tip.

The injector 21 further comprises a heat conducting shield 31 tofacilitate heat transfer away from the injector tip 25 and moreparticularly, the portion 33 of the injector tip surrounding the outletof the injector orifice 29, to the cooled injector body 23 in order tomaintain the temperature of the portion surrounding the outlet of theinjector orifice below the critical temperature, i.e., usually belowabout 180° C. The heat conducting shield comprises a heat conductingshield orifice 35 arranged coaxially with the injector orifice 29. Theheat conducting shield 31 is in direct contact with at least one of theinjector body 23 and the injector tip 25 (shown in contact with both inFIGS. 1A and 1B). The heat conducting shield 31 is shown incross-section in FIGS. 1B and 2. The heat conducting shield 31 isordinarily made of a material that is at least as conductive as thematerial from which the injector tip 25 is made. A presently preferredmaterial for the heat conducting shield 31 is copper, although othermaterials are also suitable.

The injector 21 can be a seventh injector of the type commonly used indiesel engine exhaust systems such as that shown in FIG. 3. The exhaustsystem may be of the type used in a vehicle 100 as shown schematicallyin phantom. The injector 21 can he arranged downstream of a dieselengine 37 and in or upstream of an exhaust aftertreatment component suchas a diesel particulate filter 39 (DPF). The injector 21 can be arrangedto inject fuel into the exhaust gas stream in order to e.g., raise thetemperature in the DPF 37 to regenerate the DPF. The injector 21 may beused for purposes other than raising the temperature of a DPF duringregeneration, however, that is a typical application of such aninjector.

The injector body 23 comprises a main body portion 41 and the injectortip 25 comprises a cylindrical portion 43 that extends from the mainbody portion. The cylindrical portion 43 can be generally circularlycylindrical or a series of stepped, circularly cylindrical portions asshown in FIGS. 1A-1B, which shapes can facilitate manufacturing or itcan be other shapes. To facilitate heat transfer from the cylindricalportion 43 and, more particularly, from the portion of the injector tip25 surrounding the injector orifice 29, it is typically desirable thatthe cylindrical portion is less massive than the Main body portion 41.

The heat conducting shield 31 can be in direct contact with at leastpart of the cylindrical portion 41, ordinarily at least the portion 33of the injector tip 25 surrounding the outlet of the injector orifice29, which is typically the top surface of the cylindrical portionsurrounding the injector orifice. The heat conducting shield 31 may bespaced from at least part of the cylindrical portion 41 as seen in,e.g., FIG. 1B so that the heat conducting shield may only contact thecylindrical portion at the portion 33 surrounding the outlet of theinjector orifice 29, however, the heat conducting shield may contact theentire exterior surface of the injector tip 25. The heat conductingshield 31 can also or alternatively be in direct heat conducting contactwith the main body portion 41. To facilitate heat transfer between theheat conducting shield 31 and the injector, in particular, the cooledbody portion 41 and the injector tip 25, a heat sink paste may beapplied between the heat conducting shield and the body portion and tip.

It can be desirable to limit contact of the heat conducting shield 31 todirect contact with the portion 33 of the injector tip 25 surroundingthe injector orifice 29 and with the cooled main body portion 41, andminimizing contact of the heat conducting shield at other portions ofthe injector tip, to better ensure that there is heat transfer away fromthe portion around the injector orifice to better ensure that that partof the injector tip is cooled to below the critical temperature. Thus,as seen in FIG. 1B, an empty space 45 may be provided between exteriorwall surfaces 47, 49, and 51 of the injector tip 25 and interior wallsurfaces 53, 55, and 57 of the heat conducting shield 31.

A surface of an outer side of the heat conducting shield 31, the surfaceopposite the side facing the injector 21 in FIG. 1 b, is intended to beexposed to exhaust gas and unburned hydrocarbon (fuel). To avoid exhaustgas matter and fuel horn adhering to the heat conducting shield, theexposed, outer surface of the heat conducting shield may be coated witha non-stick coating, such as Teflon® or another suitable coatingmaterial.

The heat conducting shield 31 may be secured to the injector 21 in anysuitable fashion. FIG. 1B shows the heat conducting shield 31 secured tothe injector 21 by means of an interference fit between an interiorsurface 59 of the heat conducting shield 31 and an exterior surface 61of the injector tip 25. Instead of an interference fit, the injector tip25 and the heat conducting shield 31 may have a threaded connection, orthe heat conducting shield may be secured to the main body portion 41,such as by welding, brazing, by some suitable fasteners, or by anadhesive such as epoxy.

The heat conducting shield 31 can be a variety of shapes, however, apresently preferred shape includes a first portion 63 having the heatconducting, shield orifice 35, with the heat conducting shield orificeand the injector orifice being arranged coaxially. The first portion 63can be adapted to contact the injector tip 25 by the portion 33 of theinjector tip around the injector orifice 29. A second portion 65 of theheat conducting shield 31 is separate from the first portion 63 and canbe adapted to be in direct contact with the injector body 23 and theinjector tip. The heat conducting shield 31 comprises a generallycylindrical wall 67 including interior surfaces 53, 55, 57, and 59defining an opening for receiving the injector tip 25. The secondportion 65 of the heat conducting shield 31 can comprise a flange 69disposed annularly around the first portion 63.

In a method according to an aspect of the present invention, a DPF 39 ofan exhaust aftertreatment system as shown in FIG. 3 is regenerated byinjecting fuel into or upstream of the DPF through an injector orifice(29. FIGS. 1A-2) in an injector tip (25. FIGS. 1A-2) of an injector 21.A main body (41 FIGS. 1A-1B) of the injector 21 from which the injectortip extends is cooled b circulating a coolant through a channel (27 FIG.1A) in the injector 21, Heat from the injector tip is transferred viathe heat conducting shield (31, FIGS. 1A-2) in direct contact with atleast one of the injector tip and the main body around the injector tip.The temperature of the portion 33 of the injector tip 25 around theinjector orifice 29 is kept at a temperature below a critical,temperature of about 180° C. above which diesel fuel tends to becomesticky and adhere to the injector tip, thereby reducing the possibilityof clogging. Coolant flow can be controlled to adjust the temperature ofthe portion 33 of the injector tip 25 in response to differentconditions.

Aspects of the present invention over a solution to the problem ofseventh injector clogging by preventing temperatures at the seventhinjector tip from being within the range of temperatures at which dieselfuel tends to become sticky and adhere to metal. The use of a simpleheat conducting shield on conventional seventh injectors provides asolution that involves little or no extra use of fuel to overcomeclogging problems, that is inexpensive to implement, and that is adaptedto be retrofit on existing vehicles.

In the present application, the use of terms such as “including” isopen-ended and is intended to have the same meaning as terms such as“comprising” and not preclude the presence of other structure, material,or acts. Similarly, though the use of terms such as “can” or “may ” isintended to be open-ended and to reflect that structure, material, oracts are not necessary, the failure to use such terms is not intended toreflect that structure, material, or acts are essential. To the extentthat structure, material, or acts are presently considered to beessential, they are identified as such.

While this invention has been illustrated and described in accordancewith a preferred embodiment, it is recognized that variations andchanges ma be made therein without departing from the invention as setforth in the claims.

What is claimed is:
 1. A fluid cooled injector, comprising: an injectorbody comprising an injector tip and a cooling channel, the injector tipcomprising an injector orifice; and a heat conducting shield, the heatconducting shield comprising a heat conducting shield orifice arrangedcoaxially with the injector orifice, the heat conducting shield being indirect heat conducting contact with at least one of the injector bodyand the injector tip.
 2. The fluid cooled injector as set forth in claim1, wherein the injector body comprises a main body portion and theinjector tip comprises a cylindrical portion that extends from the mainbody portion.
 3. The fluid cooled injector as set forth in claim 2,wherein the heat conducting shield is in direct contact with at leastpart of the cylindrical portion.
 4. The fluid cooled injector as setforth in claim 2, wherein the heat conducting shield is in directcontact with a top surface of the cylindrical portion surrounding theinjector orifice.
 5. The fluid cooled injector as set forth in claim 2,wherein the heat conducting shield is spaced from at least part of thecylindrical portion.
 6. The fluid cooled injector as set forth in claim2, wherein the heat conducting, shield is in direct contact with themain body portion and the cylindrical portion.
 7. The fluid cooledinjector as set forth in claim 1, wherein the heat conducting shield ismade of a material that is at least as conductive as the injector tip.8. The fluid cooled injector as set forth in claim 1, wherein thecooling channel is ring-shaped and surrounds a central passage leadingto the injector orifice.
 9. The fluid cooled injector as set forth inclaim 1, wherein the heat conducting shield includes a non-stickmaterial coating on an outer surface.
 10. An exhaust system for anengine comprising a diesel particulate filter and a fluid cooledinjector according to claim 1 upstream of the diesel particulate filter.11. A vehicle comprising an engine and an exhaust system according toclaim
 10. 12. A heat conducting shield for a fluid cooled injector, thefluid cooled injector comprising an injector body comprising an injectortip and a cooling channel, the injector tip comprising an injectororifice, the heat conducting shield comprising a first portion having aheat conducting shield orifice adapted to be arranged coaxially with theinjector orifice and a second portion, separate from the first portion,at least one of the first portion and the second portion being adaptedto he in direct contact with the injector body.
 13. The beat conductingshield as set forth in claim 12, wherein the heat conducting shieldcomprises a generally cylindrical wall defining an opening for receivingthe injector tip.
 14. The heat conducting shield as set forth in claim12, wherein the second portion of the heat conducting shield comprises aflange extending from and annularly around the first portion.
 15. Theheat conducting shield as set forth in claim 12, wherein the beatconducting shield is made of copper.
 16. The beat conducting shield asset forth in claim 12, wherein the beat conducting shield includes anon-stick material coating on an outer surface.
 17. A method ofregenerating a diesel particulate filter (DPF) in an exhaustaftertreatment System, comprising: injecting fuel into or upstream ofthe DPF through an injector orifice in an injector tip of an injector;cooling a main body of the injector from which the injector tip extendsby circulating a coolant through channels in the injector; andtransferring heat from the injector tip via a heat conducting shield indirect contact with at least on of the injector tip the main body aroundthe injector tip, and comprising a heat conducting shield orificearranged coaxially with the injector orifice.